Taking assurance from the fact that municipal-flouridation goes to "half or less" some "generally recognized safe level" implies that a low-concentration is enough for safety – "ensure your water's at that level, then have as much as you want!" – but that doesn't seem to be true.
It's total consumption that brings risks. Someone who drinks twice as much water at that presumed "safe" level is at more danger – as are those who might be getting extra flouride elsewhere, such as from higher tea consumption or excessive use of flouridated toothpastes.
Pre-2015, US flouridation standards used to be higher in colder climates, and lower in hotter climates, to account for the added water consumption in hotter climates. As of 2015, they guided everywhere to the originally-only-for-hotter-areas lower level, 0.7 mg/L, which is about half the levels with the decent evidence of harm.
But that could still be putting high-total-consumption people at unnecessary risk, and for a pretty-small benefit (fewer cavities) that can be obtained with non-ingesting tooth surface flouride exposure (as with toothpaste).
Any anti-flouridation advocate who relies on "their groundwater" rather than municipal taps probably does care about its natural concentration levels, and would only have to be concerned with moderate tea drinking if they're also receiving extra surprise flouride via municipal water. (A authentic concern for minimizing total consumption doesn't make any particular neurotic avoidance a good litmus test.)
> It's total consumption that brings risks. Someone who drinks twice as much water at that presumed "safe" level is at more danger – as are those who might be getting extra flouride elsewhere, such as from higher tea consumption or excessive use of flouridated toothpastes.
The safe levels are built around a model of the amount of water a human being can consume, both directly (drinking tap water) and indirectly (cooking, drinks made with tap water, etc.).
> for a pretty-small benefit (fewer cavities) that can be obtained with non-ingesting tooth surface exposure (as with toothpaste).
This pretty drastically understates the public health impact of fluoridation, and overstates how likely people are to apply elective equivalents (e.g. sufficient fluoridated toothpaste). The good news is that we have concrete numbers for these impacts[1], which consistently show that even developed areas show significant dental health improvements with municipal fluoridation.
>The safe levels are built around a model of the amount of water a human being can consume, both directly (drinking tap water) and indirectly (cooking, drinks made with tap water, etc.).
The epidemiological studies suggesting detectable harm at 1.5mg/L are from whatever amounts are actually consumed in affected areas, not some "model" of the max any person could consume.
Given the variety of human practices – preferences for packaged drinks, different food-preparation approaches, etc – the same tap levels could easily result in gigantic differences in net consumption among different individuals.
If the standard is half the "safe" level, but some people consume 4x or 10x as much tap water, & perhaps even have a higher baseline of non-tap-water flouride consumption, then some percentage N of the population could be developmentally-harmed, even at levels "safe" for "most". How high of an N should we accept for the modest benefit of fewer cavities?
Your link shows no public benefits other than less tooth decay, doesn't compare flouridation to other interventions, & doesn't weigh costs versus benefits.
If I'm reading its "DMFT Index" ("Decayed, Missing, Filled Teeth [per capita]") values right, it also shows a very modest benefit: a "DMFT" of 0.06 in flouridated areas, and 0.115 in non-flouridated areas. Roughly, instead of one cavity-affected-tooth per 17 kids, there's one cavity-affected-tooth per 9 kids.
Yes, we should try to minimize cavities, but what N% of outlier-consumption overflouridated kids should get a 5-IQ-point drop for that marginal benefit?
What if we shifted the flouridation expense into reminding kids to brush or use a flouridated rinse? What if we just paid a cash bonus to kids who manage to avoid permanent-tooth cavities through whatever interventions work? (The same funds would go to treatment/amelioration for those who wind up with decay anyway.)
> How high of an N should we accept for the modest benefit of fewer cavities?
You do realize dental issues kill people, right? If you are going to be actually honest in your argument, then you should be comparing the # of people that die as a result of poorer health outcomes as a result of dental complications versus the band of people having overexposure to fluoride especially since you immediately jump to the worst possible outcome on your end of the argument.
Yea, all the costs and benefits should be weighed!
I suspect a lot more people die over their lifetime from being -5 IQ than cavities. But, let's be sure all the effects are net-tallied – not just an unquantified hand-wavy "saves lives via dental health" with zero consideration to any stupidity or behavioral issues created.
1. You're presumably talking about the HHS review in your adjacent comment. Here's the actual monograph[1]. Notably, the review's authors consider it a "medium confidence" finding. In the NTP's taxonomy[2], that makes it a lower impact conclusion than the voluminous findings that show that fluoridation at 1.5mg/dL (much less 0.7mg/dL) has no adverse developmental effects.
2. The monograph is explicit about the limitations of its conclusions. In particular, the monograph explicitly says that it doesn't offer a quantitative account of fluoride-for-lost-IQ-points, and explicitly concludes that its findings do not address fluoridation at levels used in the US or Canada.
3. The monograph is focused on fluoridation at or above 1.5mg/dL, with extensive consideration given to much higher fluoridation levels.
As a whole, the monograph doesn't not present the cohesive, "closed case" for a relationship between municipal water fluoridation and developmental risk that you're suggesting exists. At best, it presents a body of evidence showing a moderate correlation between negative developmental effects and natural/dietary fluoride consumption at levels that are 5-10x times the level introduced in the US.
> If the standard is half the "safe" level, but some people consume 4x or 10x as much tap water, & perhaps even have a higher baseline of non-tap-water flouride consumption, then some percentage N of the population could developmentally-harmed, even at levels "safe" for "most".
First: neither your source (nor any source I'm aware of) shows developmental effects in adults, i.e. a general population sampling. Not even at extremely high naturally occurring fluoride levels.
However, even if we reduce to children, neither your source (nor any I'm aware of) shows a multiplicative effect to fluoridated water consumption. In other words: children in areas with 5mg/dL of naturally occurring fluoride appear to have blood levels that consistently correlate with that natural level, regardless of variations in dietary patterns. The parsimonious explanation for this is that fluoride doesn't bioaccumulate in soft tissues and is mostly excreted when not accumulated in teeth and bones, which research supports[3].
The TL;DR for this is that there's no positive evidence (and a lot of negative evidence) for differences in consumption during normal human activity having any effect on blood/urine fluoride levels. Baseline changes result in changes; volume does not.
(This ties in with the earlier point: you can definitely increase the amount of fluoride in your system over a point in time by, say, drinking 3 cups of green tea in a row. But children aren't doing that, and their most accessible equivalent - drinking water - is not something that they can chug liters of at a time.)
> Roughly, instead of one cavity-affected-tooth per 17 kids, there's one cavity-affected-tooth per 9 kids.
I personally wouldn't describe that kind of reduction as modest. On the city scale, that's thousands of dental procedures averted per year. Factored with differences in dental care (e.g. childhood cavities correlating with worse adult dental outcomes), and you have an expensive, easily preventable public health problem.
> What if we shifted the flouridation expense into reminding kids to brush or use a flouridated rinse?
Brushing reminders and basic dental hygiene are exceedingly well-messaged in developed countries. Despite that the problem remains, as evidenced by studies consistently showing differences between fluoridated and un-fluoridated populations with generally good dental practices[4].
I suppose we could always spend more on educating parents and children on good dental hygiene. But municipal fluoridation is cheap, effective, and most importantly pervasive: it addresses the last X% of the population that can't or won't practice good dental hygiene.
Just to note, the words "medium confidence" appear in neither the NTP monograph nor the taxonomy you referenced. They use the term "moderate confidence", which I guess has a similar meaning, but given the scale is from very low to low to moderate to high, I don't think this alleviates any of my concerns.
> the lower level, 0.7 mg/L, which is about half the levels with the decent evidence of harm.
Do you have a source for this claim?
This summary of a meta-analysis[1] says that there was only very weak evidence for measurable IQ harm in the range 8-16 mg/L, which is 10-20 times the recommended level. The highest quality studies in the meta-analysis showed no relationship at all between fluoride exposure and IQ[2].
> The long-awaited report released this week comes from the National Toxicology Program, part of the Department of Health and Human Services (HHS). It summarizes a review of studies, conducted in Canada, China, India, Iran, Pakistan and Mexico, and concludes that drinking water containing more than 1.5 milligrams of fluoride per liter is consistently associated with lower IQs in kids.
>The report did not try to quantify exactly how many IQ points might be lost at different levels of fluoride exposure. But some of the studies reviewed in the report suggested IQ was two to five points lower in children who had had higher exposures.
>Since 2015, federal health officials have recommended a fluoridation level of 0.7 milligrams per liter of water, and for five decades before the recommended upper range was 1.2. The World Health Organization has set a safe limit for fluoride in drinking water of 1.5.
Good summary. This is a good example of people making bijective errors around public health: the presence of a "safe level" does not itself imply that levels above it are unsafe; all it does is express confidence that the level itself is safe.
It's total consumption that brings risks. Someone who drinks twice as much water at that presumed "safe" level is at more danger – as are those who might be getting extra flouride elsewhere, such as from higher tea consumption or excessive use of flouridated toothpastes.
Pre-2015, US flouridation standards used to be higher in colder climates, and lower in hotter climates, to account for the added water consumption in hotter climates. As of 2015, they guided everywhere to the originally-only-for-hotter-areas lower level, 0.7 mg/L, which is about half the levels with the decent evidence of harm.
But that could still be putting high-total-consumption people at unnecessary risk, and for a pretty-small benefit (fewer cavities) that can be obtained with non-ingesting tooth surface flouride exposure (as with toothpaste).
Any anti-flouridation advocate who relies on "their groundwater" rather than municipal taps probably does care about its natural concentration levels, and would only have to be concerned with moderate tea drinking if they're also receiving extra surprise flouride via municipal water. (A authentic concern for minimizing total consumption doesn't make any particular neurotic avoidance a good litmus test.)